Deficiency of dystrophin-associated proteins: a common mechanism leading to muscle cell necrosis in severe childhood muscular dystrophies.

Dystrophin is a large cytoskeletal protein encoded by the Duchenne muscular dystrophy (DMD) gene. Dystrophin is associated with a large oligomeric complex of sarcolemmal glycoproteins, including the novel laminin-binding glycoprotein called dystroglycan, which provides a linkage to the extracellular matrix. In DMD, the absence of dystrophin leads to a drastic reduction in all of the dystrophin-associated proteins. In severe childhood autosomal recessive muscular dystrophy with DMD-like phenotype (SCARMD), a specific deficiency of the 50 kDa dystrophin-associated glycoprotein is found. Thus, the disruption/dysfunction of the dystrophin-glycoprotein complex due to the deficiency of one or more of the dystrophin-associated proteins is presumed to cause the disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. This may render muscle cells susceptible to necrosis in two forms of severe childhood muscular dystrophy, DMD and SCARMD.